Construction of Enantioselective Photochromic System Controlled by Chirality of the Reaction-Field

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DNA- quaternary ammonium ion complex(DNA-QAIC) was obtained by the addition of dimethyldioctadecylammoniun salt to DNA, according to the procedures previously reported. We have clarified that DNA-QAIC can be the transparent matrices of photochromic reactions.The stretched films of DNA-quaternary ammonium ion complex (DNA-QAIC) incorporating diarylethene exhibited large reversible change in optical rotation by its photochromic reactions.Diarylethenes show similar conversion ratio to their colored form in solution, regardless of the presence or absence of the hydroxyl groups in their structure. The diarylethenes showed lower reactivity in DNA-QAIC film or in organic solvents like chloroform in the presence of DNA-QAIC, than in solution without DNA-QAIC. The diarylethene with hydroxyl groups at 2-positions of the benzothiophene rings, that is 1,2-bis(2-hydroxymethyl-3-benzothienyl)hexafluorocyclopentene, showed no coloration when it is dissolved in chloroform together with DNA-QAIC. It is … More because the conformation of the diarylethene was fixed to a non-cyclizable parallel conformation. It was suggested that the diarylethene molecules were partly intercalated between the DNA base pairs.It is well-known that amioanthracene can intercalate between DNA base pairs. The diarylethene with an aminoanthracene intercalated at the anthracene moiety between the DNA base pairs in solution. As the result, fluorescence property changed to some extent, although the photochromic reaction was observed.Although the photochromic reaction were not detected for the powder of spiropyran, the powder of DNA-QAIC incorporating spiropyran showed thermally reversible photochrimism. In this case, the spiropyran in the powder were considered to be intercalating into the DNA-QAIC, and DNA-QAIC can be the transparent matrices of photochromic reactions. The thermal decoloration reactions of spiropyrans in DNA-QAIC films was slower, and the absorbance at the photo-thermo-stationary state was smaller than those in polystyrene films. The structure and the motion of spiropyrans doped in the DNA-QAIC films were restricted, so that it was difficult to change to the corresponding merocyanine form. Less